Process and device for preparing meals

ABSTRACT

Frozen meals are placed in a hermetically sealable cooking space (2) in which explosion-like puffs of steam are produced. Before the puffs of steam are produced, the air present in the cooking space can be heated. The puffs of steam are produced by evaporation of dosed quantities of water. Water is introduced into the cooking space (2) through a nozzle (40) which opens into the cooking space. The means can be regenerated or even cooked with the greatest possible care in the shortest possible time without detriment to their quality.

The present invention relates to a process for preparing meals and to adevice for carrying out this process.

When a number--or even a large number--of people have to be served withmeals within a short space of time, it is quite usual for the meals tobe prepared in advance, deep-frozen or chilled in individual-sizedportions, and only regenerated immediately before serving. In suchsituations it is important that the food can be regenerated in theshortest time possible. Steam can be used for the regeneration process,since it contains a great amount of thermal energy. The frozen orchilled food is, however, enclosed in sealed containers so that thesteam cannot penetrate to the food itself. The times required for theregeneration by means of steam are too long in terms of the givensituation.

The object of the present invention is to indicate a process whicheliminates the stated disadvantage.

According to the invention, the stated object is achieved in the processof the generic type mentioned in the introduction as is defined in thedefining clause of claim 1.

A device suitable for carrying out this process is defined in thedefining part of claim 7.

Embodiment possibilities of the present invention are explained ingreater detail below with reference to the attached drawing, in which:

FIG. 1 shows the main part of the present device in a front view,

FIG. 2 shows as a diagram and in a vertical section a container,representing a further component of the present invention and

FIG. 3 shows in horizontal projection the container according to FIG. 2.

The part of the present device for preparing meals represented in FIG. 1has an oven. This oven includes a virtually parallelepiped casing orshell 2, which delimits a cooking space for the food to be prepared. Oneof the walls of the casing 2 is manufactured as a door; in the modelshown this is the front wall 3. The casing 2 also includes four lateralwalls 4, 5, 6 and 7, as well as a rear wall 8.

The walls 3-8 of the casing have an outer envelope and an inner envelope(not shown), which are made of an impact resistant material, e.g. metal.Between these layers is a thermally insulating material of known type.The walls of the casing 2 are consequently relatively thick, as can beseen from the lateral walls 4, 5, 6 and 7 of the casing 2 in thedrawing.

The door 3 allows access to the cooking space so that the food to beprepared can be loaded and unloaded. The door is constructed in such away that it can be hermetically or pressure sealed. This is especiallyimportant in the present case since there is considerable overpressurein the cooking space at certain times while the oven is working. Inorder to make it possible to vacuum seal the cooking space, aself-contained strip 9 of a flexible material is attached to the insideof the door 3 and projects from the inside surface of the door. Thissealing strip 9 is fixed to that part of the inside of the door 3opposite the surface already mentioned of the lateral walls 4-7. Whenthe door 3 is closed the sealing strip 9 lies tight against the surfaceof the lateral walls 4-7 of the casing 2.

Hinges are fixed in the region of one of the vertically running lateralwalls 7 of the casing 2. These hinges are basically in the form ofmaterial strips attached to the surface of the horizontal casing walls 4and 6, for instance by means of screws. These hinges 11 and 12 are closeto the outside edge, respectively to the outer envelope, of the casingwall 4 or 6 respectively and are relatively narrow. The hinges 11 and 12have an eyelet-shaped section 13, respectively 14, which projects fromthe outside of the vertical lateral wall. The eyelet sections 13 and 14can be bent out of the plane of the surface of the lateral walls 4 -7 inorder to be able to compensate for the thickness of the sealing strip 9.

The height of the door 3 is less than the height of the vertical walls 5and 7 of the casing by at least twice the width of the strip-shapedhinges 11 and 12. There is thus room for one of the vertical borders ofthe door 3 between the hinge strips 11 and 12, particularly between theeyelet-shaped sections 13 and 14 of the same. At those points of thehorizontal edge of the door 3 that are near the eyelets 13 and 14, thereare pegs 15 and 16 which project vertically from the edge of the door.These pegs 15 and 16 are surrounded or held by the eyelets 13 and 14 ofthe hinges 11 and 12 so that the door 3 can be swivelled on the axisthat passes through the pegs 15 and 16.

Snap-catches 17 and 18 for the door 3 are fixed onto the surface of theopposite casing wall 5, which is also vertical. These catches 15 and 16are constructed as rollers in the model shown, with a virtuallyhorizontal axis. The rollers in the oven casing are on a spring and canbe swivelled out vertically from their original position. The catches 17and 18 are very near to the outer edge, or outer shell respectively, ofthe horizontal walls 4 and 6. There are recesses in the edge surfaces ofthe vertical border of door 3 (opposite the hinged edge) where therollers of the catch 17, respectively 18, can fit in.

Inside the cooking space and inside housing 2 respectively, there is aheating element 20, which advantageously is an electrical heater. Theheating element 20 is attached to the inside of one of the casing'ssecured walls. In the example given, the heating element 20 is on theinside of and a distance away from the rear wall 8 of the casing. Totransfer thermal energy to the cooking space as quickly as possible, theactual heating element 20 is virtually zigzag shaped to considerablylengthen the element. The curves of the zigzag form lie in a plane whichis virtually parallel to the rear wall 8 of the casing. The heatingelement 20 is situated in the lower area of the cooking space, as it isknown that warm air and superheated steam rise.

The feeder legs 21 and 22 are connected to the actual heating element.Feeder pipes are situated in these feeder legs 21 and 22, leading to theheating element 20. These feeder legs run virtually in a straight lineand reach up from the heating element, where they join together in themiddle section of the oven casing. In this oven section, an outlet 23 ismade in the casing rear wall 8. The feeder legs 21 and 22 leave theinterior of the casing through this outlet 23. The outlet has a plate 24with a circular outline. The thickness of this plate is about the sameas the rear wall 8 of the oven and can be sealed into the rear wall 8.To this end a screw thread can be added to the exterior wall of theoutlet-plate 24, which can be screwed into a corresponding thread in therear wall 8.

The amount of thermal energy within the cooking space can be increasedfurther by using several of the aforementioned heating elements. In thedepicted example, three similar heating elements 20 are placed alongsideor above each other. The drawing depicts the feeder legs 211, 212, 213and 221, 222, 223 respectively. These feeder legs 211 to 223 bend off atdifferent angles with respect to the vertical legs 21 and 22, so thateach can be assigned a separate route into the outlet 23.

A bracket is needed to position, then to secure, the heating element 20.This bracket surrounds a yoke, which takes the form of a small rail. Asecond small rail (not depicted) is assigned to the yoke and liesbetween the casing rear wall 8 and the yoke 26. The straight legs 21 and22 of the heating element 20 are situated between the above-mentionedmain rail and the yoke 26. The yoke 26 and the main rail are fixed tothe rear wall 8 with screws. If several heating elements 20 are to behoused in the cooking space, they should lie next to each other in themanner described above. In that case, intermediate rails (not depicted)are situated between the individual heating elements 20. There can berecesses on the yoke 26 and the other rails of the bracket 25, in whichthe feeder legs 21 and 22 can sit.

Inside the cooking space there is also a thermometer sensor 30. Thethermometer sensor 30 is assigned to the plate 24 of the outlet 23,below the connecting passages of the heating element feeders 211 to 223,thus keeping to a minimum the effect on it of the heat produced in theheater feeders. The lines of the thermometer sensor 30 leading outsidego through the plate 24 of the outlet 23. There is also a pressure gaugesensor 31 in the cooking area. The pressure gauge sensor is alsoassigned to the plate 24 of the outlet 23 and the lines of this sensor31 leading outside also go out through the plate 24 of the outlet 23.

The lines of the thermometer gauge sensor 30 and the pressure gaugesensor 31 that lead to the outside are connected to a controlling device35, which is on the exterior of the housing rear wall 8. Thiscontrolling device 35 forms another component part of the presentappliance and is assigned outside the cooking space.

The appliance also has a ventilator 36, which can be controlled by thecontrolling device 35. This ventilator 36 contains a turbine wheel 37,which is secured to the shaft of a deck motor. The turbine wheel isinside the cooking space, while the motor is assigned outside thecooking space. The turbine wheel 37 is placed as close as possible toone of the fixed walls of the oven casing. In the depicted example, theventilator 36 is assigned to the rear wall 8 of the oven.

The turbine wheel 37 can have a disc 38 secured to the center of theprimary shaft. This disc 38 can be built into the oven wall. There areridges 39 on the surface of the disc 38 which faces into the cookingarea. The ridges stand clear of the surface and run in an arch shape.The tangents to the middle of such a ridge form a 45 degree angle withthe tangents in this section of the perimeter of the disc 38.

The deck motor of the ventilator 36 is located outside the cookingspace, so that the main shaft goes through the appropriate wall 8 of theoven housing. The penetration point of the deck motor is air tight. Themain purpose of the turbine wheel 37 on the shaft is to circulate theair and steam in the cooking space. This circulation means thetemperature in the cooking space is virtually constant throughout thepreparation of the food.

A nozzle 40 leads into the cooking space, through which water can bechannelled into the cooking space. This nozzle is set into the plate 24of the outlet 23 and the end of the nozzle outside the cooking space isconnected to a water source. This source (not depicted) is also outsidethe cooking space and is controlled by the controlling device 35. Thewater source is set up in such a way that small doses of water can beforced into the cooking space through the nozzle 40. The water sourcecontains a pump, which can release fixed doses of water.

The nozzle 40 can be arranged in such a way that the nozzle opening isdirected into the interior of the cooking space. The nozzle 40 canhowever also be arranged so that it is directed against one of thecomponents of the cooking space, which can create water vapour or steamfrom the water being sent through. If the nozzle 40 is directed againstthe turbine wheel 37 of the ventilator 36, the water entering thecooking space by means of a jet through the nozzle 40 is changed intowater vapour through the rotating turbine wheel 37. This water vapourquickly changes to steam because of the heaters 20 located in thecooking space. If the nozzle 40 is directed against the heaters 20, thewater is changed into steam immediately.

In addition to the opening in the oven housing which can be closed bymeans of door 3, there is a second opening 41 which is a channel intoone of the walls 4 to 8 in the oven casing. The profile of this channel41 is small but the size of this cross-section is variable. For the sakeof simplicity, the opening 41 is shown on the diagram to be in theceiling 4 of the cooking space. The size of the cross-section of opening41 can be adjusted using the control valve 42 of a type known in theart. On the example given, this valve 42 is assigned to the outer mouthof opening 41. The valve 42 is connected to the controlling device 35and the size of the cross-section of the channel 41 is adjusted on thebasis of commands given by the controlling device 35. The valve 42 canbe built into the casing of the cooking space, advantageously in one ofthe fixed walls. The sealable channel 41 provides a connectioncontrolling the flow of air between the interior of the cooking spaceand the surroundings of the present appliance.

The controlling device 35 is designed to control the interaction of theindividual component parts of the present appliance. The controllingdevice 35 also contains a mechanism for determining periods of time,i.e., a clock or timing pulse generator (not depicted). Such mechanismsare known in the art and are easily obtainable.

The present device also includes containers 50 to hold the food to beprepared. One of these containers is shown in diagrammatic form in FIG.2 and 3. The container 50 has a lower part 51 and a lid 52, and thereare perforations 53 in the lid. The lower part of the container 51 has abase 54 and a wall 55, the wall 55 being connected to the edge of thebase 54. There are devices 56 on the free edge of the container wall 55to hold the lid 52 onto the lower part 51. These devices 56 can take theform of a strip of material all around the periphery which encompassesthe edge of the lid 52. The perforations 53 can also be in wall 55and/or in floor 56 of the container 50, as shown in simple diagrammaticform in FIG. 2. Steam can enter the container 50 via the perforations 53and then penetrate the spaces between the ingredients inside eachcontainer. The containers 50 can be placed on the floor 43 of thecooking space and/or on a suitable stand or additional floor (notdepicted) located in the cooking space.

Food is placed in the cooking space, the cooking space is made air tightby closing door 3 and, by means of a control button on the controllingdevice 35, the required manner of preparation of the food within thecooking space is selected.

While the food is being prepared, explosion-like bursts of steam can beseen within the cooking space. These bursts of steam cause a suddenincrease in the pressure within the cooking space, which encourages thesteam to penetrate as far as the food within each bowl. As alreadystated, in this manner steam can enter the spaces between the food andingredients respectively within the container, as it is well known thatmost foods have an uneven surface, with cracks or fissures. Furthermorethere are also gaps between the ingredients within the container.

Before the first jet of steam, it is advisable to warm the air withinthe cooking space. This is achieved by means of the previously mentionedheaters. The above-mentioned valve is closed during this heating phaseso that there is no flow of air between the interior of the cookingspace and the exterior of the present appliance. As the air inside thecooking space is heated, the pressure inside the air-tight cooking spaceis increased. The warming of the air inside the cooking space begins tohave an effect on the food inside, which is still frozen. The surfacelayer of the food is thawed.

This warming-up or heating phase is ended as soon as the thermometerregisters a temperature of about 90 to 100 degrees Centigrade. Wherefood only needs regenerating, this warming-up phase ends when atemperature of about 90 degrees Centigrade is reached. When food needsbaking, toasting, steaming etc. the warming-up phase ends when thetemperature reaches about 100 degrees Centigrade.

At the end of the warming-up phase, the valve can be opened to allowair, which may be mixed with the moisture produced while the surfacelayer of the food was thawing, to escape out of the cooking space viathe channel in the valve, until the pressure in the cooking space isapproximately equal to the ambient pressure. When this ambient pressureis reached, it is registered by the above-mentioned pressure sensor inthe cooking space which transmits a corresponding signal to the controldevice. As a result of this signal, the sealable channel in the casingof the cooking space, i.e. the valve, is closed and puffs of steam canstart being produced in the cooking space.

In certain circumstances, it may be more convenient to keep the valveopen during the warming-up phase. This valve, respectively the openingin it, is closed when a previously set temperature is reached, and puffsof steam can start being produced in the cooking space.

In order to produce puffs of steam, water is introduced into the cookingspace via the nozzle. This can be achieved by injecting water into thecooking space. The water may, however, also be introduced into thecooking space in the form of water vapour, i.e. sprayed. In these cases,the jet of water is simply directed against the inside of the cookingspace. As the air in the cooking space is at the stated relatively hightemperature, the injected or sprayed water turns into steam inside thecooking space.

In certain applications with this process, it is convenient for thewater jet sprayed into the cooking space via the nozzle to be directedagainst one of the component parts of the cooking space. These componentparts can convert the water into water vapour and/or steam. If water issprayed against the turbine wheel of the ventilators, the rapid rotationof the wheel first causes it to turn into water vapour which is thenconverted into steam, due to the high temperature inside the cookingspace. If the water is directed against the heating element, itimmediately turns into steam.

It is clear that steam can also be produced outside the cooking spaceand the steam thus produced can then be introduced into the cookingspace through the nozzle. This may be convenient in certain cases wherethis process is applied. However, for this, a second heating element isrequired which must be fitted outside the cooking space.

When steam is produced, the pressure suddenly increases in the cookingspace, which is now once more hermetically sealed, thus causing thepuffs of steam previously mentioned. The peak pressure can rise to 0.7bar. In order to produce such puffs of steam, measured doses of watercan be introduced into the cooking space. Such a dose can, for instance,contain 2 to 3 grams of water or even less. Such small doses of watercome from the above-mentioned water source to which the nozzle isattached. The more water is introduced into the cooking space, the morethe over-pressure inside it increases, since it is assumed that theheating element can produce sufficient heat, and the longer theover-pressure in the cooking space is maintained during this time. Thesteam inside the cooling space transmits part of its heat to the foodand condenses. The fall in the temperature of the steam also causes,among other things, a drop in pressure in the cooking space.

The pressure inside the cooking space is monitored by the previouslymentioned pressure gauge. When the pressure in the cooking space dropsto a previously set figure, e.g. to 0.025 bar, another dose of water isinjected into the cooking space and converted into steam. The time lapsebetween two consecutive injections of water into the cooking space maybe 10 seconds, for instance. The length of this interval is generallyvariable and in most cases increases from one injection to the next.This is because the food is getting warmer and warmer while it is beingsteam-treated, so that it absorbs the heat transmitted by the steam moreand more slowly. If it is considered preferable to maintain a constantinterval between injections throughout the entire process, the amount ofwater required to produce the consecutive puffs of steam can be reducedcorrespondingly.

If, at the end of the food processing, the production of another puff ofsteam depends only on a given drop in pressure inside the cooking spacehaving been produced by the previous puff of steam, the previouslymentioned device for measuring time intervals can measure the time thatelapses between two consecutive puffs of steam. If this interval exceedsa given set time it can be concluded that the food-processing isfinished. The monitoring device then automatically stops the productionof any more puffs of steam. The length of time during which food issubjected to the puffs of steam can, however, also be set to a definitevalue for particular kinds of processing and food, so that theproduction of puffs of steam automatically stops once this time is up.At the end of the processing, it is advisable for the opening in thecasing around the cooking space to remain closed.

It is possible to achieve a more intensive treatment of the food bybriefly opening the orifice-in the casing of the cooking space beforeinjecting the next dose of water, so that the pressure in the cookingspace drops to equal the ambient pressure. This means that the pressurein the cooking space can drop to that of its surroundings as long as thecooking space is thus open. Afterwards the opening in the casing of thecooking space, e.g. the valve, is closed and another dose of water canbe injected into the cooking space.

The moment at which the orifice in the cooking space casing istemporarily opened can, however, also be linked to a pre-set interval oftime elapsed since the last previous injection of water.

It also depends on the particular program selected for the foodprocessing as to how long the interval must be between two consecutivetemporary openings of the valve. The number of puffs of steam to whichthe food is subjected also depends, among other things, on the kind ofprocessing required, the type and the amount of food being processed,etc. The relevant data for a given case can be entered by means of akeyboard known in the art of similar situated on the controlling device.The controlling device then automatically carries out the actualprocessing.

If the food is not intended to be served immediately after theprocessing is finished, it is most advisable to leave it standing in thecooking space. There is a residual heat here which keeps the food warmand there is also a certain amount of residual moisture inside thehermetically sealed cooking space which keeps the food fresh.Consequently it is advisable to remove the food from the cooking spaceonly just before serving it.

In order to process the food even more intensively, the opening in thecooking space casing can be opened several times for a relatively briefperiod between two consecutive puffs of steam. This accelerates the dropin pressure in the cooking space and permits fresh hot steam to beintroduced sooner into the cooking space. When the cooking space isbriefly opened in this way, it is true that some of the steam alreadyinjected, which is still relatively hot, escapes, but it enables thenext, more energy-laden burst of steam to be introduced more quicklythan having to wait until all the thermal energy available in the amountof steam already introduced has been transmitted to the food in thehermetically sealed cooking space. By repeatedly and briefly opening thecooking space valve in this way, the amount of thermal energy requiredto process the food can be transmitted to the food in a shorter periodof time. The overall time needed to process the food in the cookingspace is thus reduced. This can result in a reduction of up to 30% ofthe time required for the transfer of heat without repeatedly openingthe cooking space valve.

The heating inside the cooking space can also be switched on between twopuffs of steam. In this case, the heating provides the steam withadditional thermal energy which can be used to treat the food.

The rotation of the turbine wheel not only ensures that the steam isuniformly distributed in the cooking space, but also that thecirculating steam flows over the food and streams into the containersthrough the openings.

The explosion-like puffs of steam produce sudden increases in pressurein the cooking space, thus creating favorable conditions for theenergy-laden steam to penetrate the food to be processed.

In the present process, using the present device, it is possible notonly to regenerate frozen or chilled foodstuffs but also to cook freshlyprepared dishes. The freshly prepared dishes can, for instance, bebaked, toasted, steamed etc.

In the present process, using the present device, food can beregenerated or even cooked in the most gentle way, in the shortest timeand with no detrimental effects on the quality. Since only small amountsof steam are effective in the cooking space and since the overall effecton the food depends on the overall number of individual little doses ofsteam, the amount of thermal energy can be adapted very precisely in thecooking space with no trouble. In these circumstances, it is easy toavoid overcooking the food, for example.

I claim:
 1. A process for the preparation of foodstuff, said processcomprising the steps of:placing the foodstuff in a cooking space;hermetically sealing the cooking space; and producing bursts of steam inthe cooking space so as to cause a sudden increase in pressure withinthe cooking space of sufficient magnitude that steam penetrates thefoodstuff.
 2. A process as in claim 1, wherein the peak pressure in thecooking space rises to 0.7 bar upon production of a burst of steam.
 3. Aprocess as in claim 1, wherein a subsequent burst of steam is producedwhen the pressure in the cooking space drops to a first predeterminedlevel.
 4. A process as in claim 3, wherein said predetermined level is0.025 bar.
 5. A process as in claim 2, further comprising the step ofinterrupting the hermetical seal between at least two subsequent burstsof steam.
 6. A process of claim 5, wherein the hermetical seal isinterrupted for a sufficient length of time to reduce the pressure inthe cooking space to a second predetermined level.
 7. A process as inclaim 6, wherein said second predetermined level is ambient pressure. 8.A process as in claim 5, wherein the hermetical seal is interruptedafter a predetermined period of time from a burst of steam.
 9. A processas in claim 1, further comprising the step of heating the cooking spacebetween two bursts of steam.
 10. A process as in claim 1, wherein burstsof steam are produced at predetermined intervals, and wherein saidintervals become longer as said foodstuff becomes warm, and wherein saidprocess is terminated when said intervals exceed a given set time.
 11. Aprocess as in claim 1, wherein said process is terminated after apredetermined number of bursts of steam have occurred.
 12. A process asin claim 1, wherein bursts of steam are produced at predeterminedintervals, and wherein the amount of steam contained within successivebursts is reduced.
 13. A process as in claim 1, further comprising thestep of circulating steam within the cooking space.
 14. A process as inclaim 1, wherein steam is produced by introducing measured doses ofwater into the cooking space, whereby the more water which isintroduced, the greater an over-pressure inside the cooking space isproduced, and the longer the overpressure is maintained.
 15. A processas in claim 1, wherein water is injected or sprayed into the cookingspace, and wherein the water is directed against an inside wall of thecooking space.
 16. A process as in claim 1, wherein water is injected orsprayed into the cooking space, and wherein the water is directedagainst a component part of the cooking space.
 17. A process as in claim1, further comprising the step of heating the air within the cookingspace before the first burst of steam is produced.
 18. A process as inclaim 1, wherein the foodstuff is frozen, and wherein said processquickly thaws the frozen foodstuff.
 19. A device for the preparation offoodstuff, said device comprising:a hermetically sealable cooking spacedefined by a casing; a first opening formed in said casing to allowloading and unloading of foodstuff; an outlet formed in a wall of saidcasing, said outlet having a plate with a nozzle through which water orsteam can be directed into said casing; and at least one heating elementdisposed within said casing, the at least one heating element havingfeeder legs extending through said plate.
 20. A device as in claim 19,wherein the nozzle has an outer end extending outside of said cookingspace, said outer end being connected to a water source so that smalldoses of water or steam can be forced into the cooking space via thenozzle.
 21. A device as in claim 19, further comprising a thermometerand a pressure sensor disposed within said cooking space.
 22. A deviceas in claim 21, wherein said thermometer is disposed below connectingpassages of the feeder legs.
 23. A device as in claim 21, wherein saidthermometer and said pressure sensor are disposed on said plate.
 24. Adevice as in claim 19, further comprising a second opening formed in awall of the casing, wherein the cross-section of said second opening isadjustable.
 25. A device as in claim 24, wherein said second openingcomprises a channel passing through a wall of said casing, and furthercomprising a valve disposed in said channel which adjusts thecross-section of said channel.
 26. A device as in claim 19, furthercomprising a ventilator having a turbine wheel, said turbine wheel beingdisposed within said casing.
 27. A device as in claim 19, furthercomprising control means for controlling the function and collaborationof elements of said device.
 28. A device as in claim 19, wherein saidnozzle is arranged in such a way that an opening of the nozzle isdirected into the interior of the cooking space.
 29. A device as inclaim 19, wherein said nozzle is arranged in such a way that an openingof the nozzle is directed against one of a component part of the cookingspace.
 30. A device as in claim 19, wherein said plate has a circularoutline, the thickness of the plate being substantially the same as thethickness of the wall of the casing in which the plate is sealed,wherein an exterior wall of said plate has a screw thread, and whereinthe plate is screwed into a corresponding thread in said wall of thecasing.
 31. A device as in claim 19, wherein the foodstuff is containedwithin a container, said container having a lower hollow part and a lid,the lower hollow part having means for holding the lid, and wherein atleast said lid has perforations through which steam can penetrate insidesaid container.
 32. A device as in claim 31, wherein said perforationsare formed in a wall of said container.
 33. A device as in claim 32,wherein said perforations are formed in a floor of said container.